1. Field of the Invention
The present invention is broadly concerned with processes for the production of polyols from proteinaceous and/or fibrous (e.g., lignin) components, and processes for reacting such polyols with isocyanates to produce polyurethanes. More particularly, the invention is concerned with processes wherein a proteinaceous component, and especially a distillers grain product, is reacted with an amine under conditions to generate amino-amides and amides from the protein and lignin fractions of the distillers grain product, and thereupon reacting such aminated products with an alkoxylating agent to generate polyols. Alternately, lignin from any source such as pulp byproducts may be directly alkoxylated to form lignin polyols. However produced, the polyols may then be recovered or reacted with isocyanates to yield polyurethanes.
2. Description of the Prior Art
Distillers grain products are byproduct materials resulting from the fermentation of starch (usually corn starch) to ethanol. These products are generally classified as wet distillers grains (WDG) and dried distillers grains with solubles (DDGS). WDG contains primarily unfermented grain residues (protein, fiber, lipids, and up to 70% moisture). Accordingly, WDG has a shelf life of only 4-5 days and, owing to the high moisture content thereof, transport is usually viable only within 20 km of the ethanol production facility. On the other hand, DDGS is a product that has been dried with concentrated thin stillage to a relatively low moisture content. DDGS has an almost indefinite shelf life and may be economically shipped to remote markets. Therefore, the primary distillers grain products are DDGS.
DDGS contains from about 28-32% protein, from about 9.4-11% lipid, from about 32-40% neutral detergent fiber (cellulose, hemicellulose, lignin), from about 15.2-17.9% acid detergent fiber, from about 9-11.8% starch, from about 4-13.2% ash, and from about 10-12% water, where all percentages are on a weight basis, with the total weight of the DDGS being 100% by weight. The high levels of nutrients in DDGS are digestible, and are useful for animal feeds. Accordingly, it is well known that DDGS are used in beef and dairy diets, and in swine and poultry diets as well. It is also noteworthy that DDGS contain many hydroxyl- and amino-containing compounds.
Lignin is the second most abundant source of carbon on earth, after cellulose and hemicellulose. Lignin is available in enormous quantities as a result of pulp industry practices, but only 1-2% from lignin is used for technical applications (binders, surfactants, phenol-formaldehyde resins etc.). The remainder of the lignin is used primarily as a fuel source. Lignin is present in DDGS in small quantities, around 3-4% by weight, and has phenolic and aliphatic hydroxyl groups.
A review of the prior art reveals only two processes for the transformation of DDGS into liquids, namely Xu et al., Liquifaction of Corn Distillers Grains with Solubles (DDGS) in Hot Compressed Phenol, Bioresources, 3(2), 363-382 (2008), and Yu et al., Atmospheric Pressure Liquifaction of Dried Distillers Grains (DDG) and Making Polyurethane Foams from Liquified DDG, Appl., Biochem Biotechnol, 148:235-243 (2008). The latter article teaches that dried distillers grains were treated under acidic conditions at atmospheric pressure, using ethylene carbonate or ethylene glycol as solvents and with sulfuric acid catalyst. The resultant polyols were separated and treated with methylene diphenyl diisocyanate in the presence of catalyst, surfactant, and blowing agent, in order to produce polyurethane foam.